why did gus kill victor

Gus Fring killed Victor primarily because Victor was spotted at the scene of Gale Boetticher's murder, which put their entire operation at risk. Victor arrived too late to stop Jesse from killing Gale, but was seen by neighbors entering and leaving the apartment, and even left his car at the scene, making him a liability that could lead police directly to Gus' operation. Gus, being a meticulous and cautious criminal, decided that Victor's survival posed too great a risk. Additionally, Gus' killing of Victor was a calculated, brutal message to Walter White and Jesse Pinkman to show them the consequences of putting the operation at risk. By killing Victor with his own hands, Gus demonstrated his cold resolve and ability to enact swift punishment, warning Walt and Jesse that their disobedience could lead to their deaths as well. Victor's death symbolized that no amount of loyalty could excuse recklessness or mistakes in Gus' eyes. Gus kept Walt and Jesse alive despite their defiance because their partnership was critical to producing the highest-quality meth, but he couldn't tolerate Victor's reckless behavior. Victor even began cooking meth without orders, indicating he was overstepping his bounds, further justifying Gus' decision in his mind. Thus, the killing of Victor served both as a protective measure for Gus' empire and a terrifying warning to his key meth cooks.